Optical interference display panel

ABSTRACT

An optical interference display panel is disclosed that has a substrate, an optical interference reflection structure, and an opaque protection structure. The optical interference reflection structure has many color-changeable pixels and is formed on the substrate. The opaque protection structure is adhered and fixed onto the substrate with an adhesive and encloses the optical interference reflection structure between the substrate and the opaque protection structure. The opaque protection structure blocks and/or absorbs light, and light is thus not emitted outward by passing through defects in the optical interference reflection structure Moreover, the opaque protection structure and the adhesive also prevent the optical interference reflection structure from being damaged by an external environment.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. application Ser. No. 11/368,683 filed Mar.7, 2006, which is a divisional of U.S. application Ser. No. 10/807,147filed Mar. 24, 2004, which claims priority to Taiwanese Application TW92122566 filed Aug. 15, 2003. Each of the above applications isincorporated by reference hereby in its entirety.

BACKGROUND OF THE INVENTION

1. Field the of Invention

The present invention relates to a display panel. More particularly, thepresent invention relates to an optical interference display panel.

2. Description of Related Technology

Due to being lightweight and small in size, a display panel is favorablein the market of portable displays and displays with space limitations.To date, in addition to liquid crystal display (LCD), organic lightemitting diode (OLEO) and plasma display panel (PDP) modules, a moduleof the optical interference display has been investigated.

U.S. Pat. No. 5,835,255 discloses a modulator array, that is, acolor-changeable pixel for visible light which can be used in a displaypanel. FIG. 1A illustrates a cross-sectional view of a prior artmodulator. Every modulator 100 comprises two walls, 102 and 104. Thesetwo walls are supported by posts 106, thus forming a cavity 108. Thedistance between these two walls, the depth of cavity 108, is D. Thewall 102 is a light-incident electrode which, according to an absorptionfactor, absorbs visible light partially. The wall 104 is alight-reflection electrode that is flexed when a voltage is applied toit.

When the incident light shines through the wall 102 and arrives at thecavity 108, only the visible light with wavelengths corresponding to theformula 1.1 is reflected back, that is,2D=Nλ  (1.1)

-   -   wherein N is a natural number.

When the depth of the cavity 108, D, equals one certain wavelength λ₁ ofthe incident light multiplied by any natural number, N, a constructiveinterference is produced, and a light with the wavelength λ₁ isreflected back. Thus, an observer viewing the panel from the directionof the incident light will observe light with the certain wavelength λ₁reflected back at him. The modulator 100 here is in an “open” state.

FIG. 1B illustrates a cross-sectional view of the modulator 100 in FIG.1A after a voltage is applied to it. Under the applied voltage, the wall104 is flexed by electrostatic attraction toward the wall 102. At thismoment, the distance between the walls 102 and 104, the depth of cavity108, becomes d and may equal zero.

The D in the formula 1.1 is hence replaced with d, and only the visiblelight with another certain wavelength λ₂ satisfying the formula 1.1produces a constructive interference and reflects back through the wall102. However, in the modulator 100, the wall 102 is designed to have ahigh absorption rate for the light with the wavelength λ₂. Thus, theincident visible light with the wavelength λ₂ is absorbed, and the lightwith other wavelengths has destructive interference. All light isthereby filtered, and the observer is unable to see any reflectedvisible light when the wall 104 is flexed. The modulator 100 is now in a“closed” state, i.e. a dark state.

As described above, under the applied voltage, the wall 104 is flexed byelectrostatic attraction toward the wall 102, such that the modulator100 is switched from the “open” state to the “closed” state. When themodulator 100 is switched from the “closed” state to the “open” state,the voltage for flexing the wall 104 is removed, and the wall 104elastically returns to the original state, i.e. the “open” state orlight state, as illustrated in FIG. 1A.

The light-reflection electrode (the wall 104) is a membrane, typicallymade of metal, and generally is manufactured with a “sacrificial layer”technique widely used in the production of micro electro mechanicalsystems (MEMS). The light-reflection electrode is very thin and iseasily damaged by even a tiny external force or by errors occurringduring manufacturing, inhibiting it from functioning properly.

For example, the light-reflection electrode may receive defects by beingtouched during manufacturing or transporting procedures. Acolor-changeable pixel containing defects is unable to reflect theincident light at defect locations. Moreover, an observer is able tolook through the defects at things behind the optical interferencedisplay panel, such as circuit boards or even light from another lightsource.

When the color-changeable pixel containing defects is operated in thedark state, the light from another light source behind it may passthrough the defects and be emitted outward so as to make thecolor-changeable pixel act in an undesired “light” state. Furthermore,after passing through the defects, the original incident light isreflected by the things behind the color-changeable pixel, such as metallines on the circuit board. The reflected light is directly emittedoutward without being filtered by the color-changeable pixel, thuscausing another undesired appearance of a “light” state. These undesired“light” states of the color-changeable pixel resemble bad pixels on theoptical interference display panel.

Display panel contrast is typically defined as a ratio of the brightnessof the “light” state to the “dark” state. The optical interferencedisplay panel totally comprises a plurality of color-changeable pixels.Therefore, the color-changeable pixels having defects which cause badpixels lower the contrast and the display performance of the displaypanel.

SUMMARY OF CLEAR INVENTIVE ASPECTS

It is therefore an objective of the present invention to provide anoptical interference display panel which mitigates the bad pixels causedby the defects in the optical interference reflection structure.

It is another objective of the present invention to provide an opticalinterference display panel which enhances the contrast of the opticalinterference display panel.

It is still another objective of the present invention to provide anoptical interference display panel that protects an optical interferencereflection structure therein from being damaged by an externalenvironment.

It is still another objective of the present invention to provide anoptical interference display panel that enhances the display performancethereof, increases its reliability, and prolongs its lifetime.

In accordance with the foregoing and other objectives of the presentinvention, an optical interference display panel is provided. Theoptical interference display panel has a substrate, an opticalinterference reflection structure, and an opaque protection structure.The optical interference reflection structure has many color-changeablepixels and is formed on the substrate. The opaque protection structureis adhered and fixed onto the substrate with an adhesive and thusencloses the optical interference reflection structure between thesubstrate and the opaque protection structure. The opaque protectionstructure blocks and/or absorbs light, and light is thereby not emittedoutward by passing through defects in the optical interferencereflection structure. Moreover, the opaque protection structure and theadhesive also prevent the optical interference reflection structure frombeing damaged by an external environment.

According to one preferred embodiment of the invention, the opaqueprotection structure is made of an opaque material or a light absorptivematerial, such as a metal material or an opaque polymer. The opaquepolymer can be a dyed polymer, e.g. a plastic mixed with a black dye.

The optical interference reflection structure comprises a plurality ofcolor-changeable pixels. The substrate and the opaque protectionstructure are airtight to prevent the optical interference reflectionstructure from being damaged by an external environment. The opaqueprotection structure is a flat structure. The adhesive comprises amaterial such as a UV glue or a thermosetting adhesive. Moreover, theadhesive further comprises spacers. According to another preferredembodiment of the invention, the opaque protection structure can be aU-shaped structure.

According to another preferred embodiment of the invention, the opaqueprotection structure is a combination of a substrate and an opaque film.The opaque film is deposited either on the side of the substrate whichis near the color-changeable pixel or on the other side. The opaque filmis a metal film or a light absorptive film. The light absorptive film isa polymer film or a dyed film, coated on the substrate. Furthermore, thelight absorptive film can also be a multilayer film, comprised ofmetals, metal oxides and/or other materials, to block and absorb thelight.

To manufacture the invention, a first electrode and a sacrificial layerare formed in order on the substrate, and then a plurality of openingsare formed in the first electrode and the sacrificial layer. One supportis formed in each of the openings, and a second electrode is then formedon the sacrificial layer and the supports. Afterward, the sacrificiallayer is removed by a release etch process to form a cavity.

Next, an opaque protection structure is adhered to the substrate suchthat the optical interference reflection structure is positioned betweenthe opaque protection structure and the substrate. A pressing procedureis used to make the adhesion between the opaque protection structure andthe substrate closer and tighter. In addition, if the adhesive is thethermosetting adhesive, a heating procedure can be used to heat thethermosetting adhesive to solidify and fix it.

The optical interference display panel provides an opaque protectionstructure to adhere to the substrate for enclosing the opticalinterference reflection structure, thus preventing light from passingthrough defects in the optical interference reflection structure andbeing emitted outward to cause spot defects. Therefore, the inventionmitigates bad pixels in the optical interference display panel andenhances the contrast thereof.

The opaque protection structure also prevents the optical interferencereflection structure from being damaged by an external force. Moreover,the adhesive hermetically seals the optical interference reflectionstructure within the display panel, effectively preventing an externalenvironment such as water, dust or oxygen in the air, from being incontact with the optical interference reflection structure andconsequently generating electrostatic force in the structure oroxidizing it to adversely affect its optical or electrical properties.In conclusion, the invention improves the display performance of theoptical interference display panel, decreases the quantity of defectivepixels, and prolongs the lifetime thereof.

It is to be understood that both the foregoing general description andthe following detailed description are examples, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1A illustrates a cross-sectional view of a prior art modulator;

FIG. 1B illustrates a cross-sectional view of the modulator in FIG. 1Aafter a voltage is applied to it;

FIG. 2A illustrates a cross-sectional view of one preferred embodimentof the invention;

FIG. 2B illustrates a cross-sectional view of one preferred embodimentof the invention;

FIG. 2C illustrates a cross-sectional view of another preferredembodiment of the invention; and

FIGS. 3A to 3B depict a method for manufacturing the preferredembodiment in FIG. 2A.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

The optical interference display panel has a substrate, an opticalinterference reflection structure, and an opaque protection structure.The optical interference reflection structure has many color-changeablepixels and is formed on the substrate. The opaque protection structureis adhered and fixed onto the substrate with an adhesive, thus enclosingthe optical interference reflection structure between the substrate andthe opaque protection structure. The opaque protection structure blocksand/or absorbs light, and light thus is not emitted outward by passingthrough defects in the optical interference reflection structure.Moreover, the opaque protection structure and the adhesive also preventthe optical interference reflection structure from being damaged by anexternal environment.

FIG. 2A illustrates a cross-sectional view of one preferred embodimentof the invention. The optical interference reflection structure has aplurality of color-changeable pixels. For clarity and ease ofunderstanding, the following descriptions and figures use only onecolor-changeable pixel 100 to represent the optical interferencereflection structure inside the optical interference display panel ofthis preferred embodiment.

As illustrated in FIG. 2A, a flat protection structure 200 a is adheredto a substrate 110 with an adhesive 202. The substrate 110 is a glasssubstrate or a substrate transparent to visible light. The flatprotection structure 200 a reduces the possibility that an externalforce reaches the color-changeable pixel 100. Moreover, the adhesive 202seals the optical interference reflection structure between thesubstrate 110 and the flat protection structure 200 a. The adhesive 202is used to isolate the color-changeable pixel 100 from an externalenvironment and prevent it from being damaged by water, dust and oxygenin the air.

When water in the air gets into the cavity 108 of the color-changeablepixel 100, the electrostatic force caused by the water is very large(because the depth D of the cavity is very small) and thus inhibits thecolor-changeable pixel 100 from being switched successfully. When themetal film, such as the light-incident electrode or the light-reflectionelectrode of the color-changeable pixel is in contact with oxygen, themetal film is very easily oxidized, and the optical and electricalproperties of the color-changeable pixel 100 are adversely affected.

In the preferred embodiment, the adhesive 202 is not only used to adherethe flat protection structure 200 a to the substrate 110 but also toisolate the color-changeable pixel 100 from an external environment. Thehigh isolation effectively protects the color-changeable pixel 100 fromdamage. According to one preferred embodiment of the invention, when theadhesive joins the flat protection structure 200 a to the substrate 110such that the color-changeable pixel is hermetically sealed, thereliability and the lifetime of the color-changeable pixel aresubstantially increased.

The flat protection structure 200 a is made of an opaque material or alight absorptive material, such as a metal material or an opaquepolymer. The opaque polymer can be a dyed polymer, e.g. a plastic mixedwith a black dye. The adhesive 202 comprises a material such as a UVglue or a thermosetting adhesive. However, other adhesives suitable foradhering the opaque protection structure and the substrate are availableto be used in the invention and are not limited by this embodiment.

In addition, during the adhering of the flat protection structure 200 ato the substrate 110, a pressing procedure is usually used to positionthe flat protection structure 200 a and the substrate 110 closer andtighter. In order to prevent the flat protection structure 200 a fromcrushing the wall 104 of the color-changeable pixel 100, or to preventthe opaque protection structure from being shifted or tilted to thesubstrate 110 by an external force, the preferred embodiment addsspacers into the adhesive 202.

The adhesive 202 with spacers keeps a predetermined distance between theflat protection structure 200 a and the substrate 110 and prevents theflat protection structure 200 a from damaging the color-changeable pixel100. In one example of the preferred embodiment, the size of the spacersis about 100 μm, and the size of the color-changeable pixel 100 istypically less than 1 μm. Therefore, there is a very large distancebetween the flat protection structure 200 a and the wall 104, thusavoiding the foregoing possibility of being crushed.

FIG. 2B illustrates a cross-sectional view of another preferredembodiment of the invention. The flat protection structure 200 b is acombination of a substrate 212 and an opaque film 214. The opaque film214 is deposited on either the side of the substrate 212 that is nearthe color-changeable pixel 100 or on the other side of the substrate212.

According to one preferred embodiment of the invention, the opaque film214 is located on the side of the substrate 212 near thecolor-changeable pixel 100. In this configuration, the opaque film 214prevents external light from shining inward from the substrate 212 andpassing through defects in the color-changeable pixel 100 to cause badpixels. In addition, the opaque film 214 can directly absorb as well asprevent reflection of light that is passing through defects in thecolor-changeable pixel 100, thereby preventing the light from beingreflected by the substrate 212 to cause bad pixels.

The opaque film is a metal film or a light absorptive film. The lightabsorptive film is a polymer film or a dyed film, coated on thesubstrate. The light absorptive film also can be a multi-layer film,which is made of metals, metal oxides, and/or other materials, to blockand absorb the light.

FIG. 2C illustrates a cross-sectional view of another preferredembodiment of the invention. In this preferred embodiment, the opaqueprotection structure is a U-shaped protection structure 200 c. TheU-shaped protection structure 200 c is a flat structure having extendedsides. As with the previous embodiment, the U-shaped protectionstructure 200 c is adhered to the substrate 110 with the adhesive toisolate the color-changeable pixel 100 from water, dust and oxygen inthe air and also to prevent the color-changeable pixel 100 from beingdamaged by an external force.

The material of the U-shaped protection structure 200 c is an opaquematerial or a light absorptive material, or a combination of a substrateand an opaque film. The U-shaped protection structure 200 c preventsexternal tight from passing through defects in the color-changeablepixel to cause bad pixels. In addition, the U-shaped protectionstructure 200 c can directly absorb as well as prevent reflection oflight originating from defects in the color-changeable pixel, thuspreventing the light from being reflected by the protection structure200 c to cause bad pixels.

FIGS. 3A and 3B depict a method for manufacturing the embodiment in FIG.2A. Reference is made to FIG. 3A first, in which a first electrode 310and a sacrificial layer 311 are formed in order on a transparentsubstrate 309. Openings 312 are formed in the first electrode 310 andthe sacrificial layer 311, and every opening 312 is suitable for formingone support 306 therein. Next, supports 306 are formed in the openings312, and a second electrode 314 is formed on the sacrificial layer 311and the supports 306.

Reference is made to FIG. 3B, in which the sacrificial layer 311 isremoved by a release etch process, such as a remote plasma etch process,to form a cavity 316. The depth D of the cavity 316 is the thickness ofthe sacrificial layer 311. Afterward, an opaque flat protectionstructure 304 is adhered to the substrate 309 with an adhesive 308.During the adhering step, a pressing procedure is used to make theadhesion between the opaque flat protection structure 304 and thesubstrate 309 closer and tighter. In addition, if the adhesive 308 is athermosetting adhesive, a heating procedure can be used to heat thethermosetting adhesive in order to solidify and fix it.

The foregoing description explains the method for manufacturing theoptical interference display panel having the opaque flat protectionstructure. The manufacturing method for the optical interference displaypanel having the opaque U-shaped protection structure is similar and isdescribed below for added clarity.

First, an optical interference reflection structure, which comprises thefirst electrode, the second electrode and the supports therebetween, isformed on the substrate. Then, an opaque U-shaped protection structureis adhered to the substrate such that the optical. interferencereflection structure is positioned between the opaque U-shapedprotection structure and the substrate. A pressing procedure is used tomake the adhesion between the opaque U-shaped protection structure andthe substrate closer and tighter.

The optical interference display panel provides an opaque protectionstructure that is adhered to the substrate and encloses the opticalinterference reflection structure, thus preventing light from passingthrough defects in the optical interference reflection structure andbeing emitted outward to cause bad pixels. Therefore, the inventiondecreases the appearance of bad pixels in the optical interferencedisplay panel and also enhances the contrast thereof.

The opaque protection structure also prevents the optical interferencereflection structure from being damaged by an external force. Moreover,the adhesive seals the optical interference reflection structure withinthe display panel, effectively preventing an external environment, suchas water, dust or oxygen in the air, from being in contact with theoptical interference reflection structure and generating electrostaticforce or oxidizing it to adversely affect its optical or electricalproperties. In conclusion, the invention improves the displayperformance of the optical interference display panel, decreases thequantity of defective pixels, and prolongs the lifetime thereof.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A display, comprising: at least one interferometric modulator arrayon a first substrate; and an opaque protection structure attached to thefirst substrate to cover the at least one interferometric modulatorarray, wherein the opaque protection structure covers the at least oneinterferometric modulator array and prevents light from passing througha defect in the at least one interferometric modulator array.
 2. Thedisplay of claim 1, wherein the interferometric modulator arraycomprises: a first electrode; a second electrode, wherein the secondelectrode is situated in parallel with the first electrodesubstantially; and a support, located between the first electrode andthe second electrode to form a cavity, wherein the second electrodemoves in response to a voltage applied between the first and secondelectrode.
 3. The display of claim 1, wherein the opaque protectionstructure absorbs light.
 4. The display of claim 1, wherein the opaqueprotection structure is a flat protection structure.
 5. The display ofclaim 1, wherein the opaque protection structure is a U-shapedprotection structure.
 6. The display of claim 1, wherein the opaqueprotection structure comprises: a second substrate; and an opaque film,deposited on the second substrate.
 7. The display of claim 6, whereinthe opaque film is between the second substrate and the at least oneinterferometric modulator array.
 8. The display of claim 6, wherein theopaque film is a metal film or a light absorptive film.
 9. The displayof claim 1, wherein the first substrate and the opaque protectionstructure are airtight to prevent the at least one interferometricmodulator array from being damaged by an external environment.
 10. Thedisplay of claim 1, wherein the opaque protection structure is adheredto the first substrate with an adhesive.
 11. The display of claim 10,wherein the adhesive comprises spacers, and the spacers keep apredetermined distance between the opaque protection structure and thefirst substrate to prevent the opaque protection structure from damagingthe at least one interferometric modulator array.
 12. The display ofclaim 10, wherein the adhesive comprises a UV glue or a thermosettingadhesive.
 13. The display of claim 1, wherein the at least oneinterferometric modulator array is located between the first substrateand the opaque protection structure.
 14. A display, comprising: meansfor supporting a microelectromechanical system, wherein themicroelectromechanical system comprises means for modulating lighttransmitted through said supporting means; and means for covering themodulating means to prevent light from passing through a defect in themodulating means, the covering means being attached to the supportingmeans and covering the modulating means.
 15. The display of claim 14,wherein the modulating means comprises at least one interferometricmodulator array.
 16. The display of claim 14, wherein the supportingmeans comprises a transparent substrate.
 17. The display of claim 14,wherein the covering means comprises an opaque protection structure. 18.The display of claim 14, wherein the covering means is adhered to thesupporting means with an adhesive.
 19. The display of claim 14, whereinthe modulating means is located between the supporting means and thecovering means.